Atomic layer deposition (ALD) and chemical vapor deposition (CVD) are two exemplary methods used in semiconductor fabrication to deposit thin films on a substrate. ALD and CVD processes generally include introducing a process gas to a process chamber in which a substrate, such as a semiconductor wafer, is supported on a substrate support. The substrate support may be fabricated from suitable metallic materials, such as aluminum or stainless steel, or suitable non-metallic materials, such as ceramic, and may contain one or more heating elements to create one or more heating zones in the support.
In some processes, energy is supplied to the process gas to form a plasma over the substrate. The plasma contains dissociated and ionized components as well as neutral components that operate to assist the process being performed on the substrate (such as ALD, CVD, etching, and the like). Although the constituents of the plasma are beneficial for assisting or carrying out the process on the substrate, unconstrained plasma components may impinge on the substrate and/or chamber components causing damage. In addition, plasma non-uniformities may lead to non-uniform processing of substrates.
Heated ceramic substrate supports or plates have been found useful in at least ALD and CVD processing. Among the features of ceramic plates are the ability to sinter the plate with various elements contained inside the plate. For example, heater elements can be provided in the plate, and the plate may be sintered with a plasma-containing wire mesh (i.e., a mesh with characteristics conducive to containing plasma) in the plate. Conventional ceramic heater plates with plasma containing mesh ground the mesh with one rod centrally brazed to the mesh.
The one-point grounding method used in conventional ceramic heater plates may create sufficient plasma uniformity for low frequency (less than 13.56 MHz) applications. However, the inventors have observed that in high frequency plasma applications (e.g., at frequencies greater than about 13.56 MHz), the single point grounding of the mesh is insufficient to create uniform plasma.